1. Field of the Invention
The invention relates to a multi-part device for making thin-walled wax models, the device containing a lower closing plate with an arrangement of first cores, and an upper closing plate with an arrangement of second cores, and a laterally located casing for surrounding the wax model to be made.
2. Description of the Prior Art
The wax models required for producing lost-wax castings are made in multi-part devices, the so-called dies or molds. These consist, as a rule, of heat-resistant steel alloys.
After the wax model has solidified in the mold, it has to be removed therefrom. This operation constitutes the most critical stage in the entire production process because the surface-to-volume ratio of the wax model is extremely large and consequently the wax model sticks hard to the core walls of the mold. Since the shaping of the wax model takes place via the liquid/solid phase or, bypassing the liquid phase, in the pasty state at temperatures below the liquidus temperature, relatively high contraction values of the wax and correspondingly greater adhesion of the wax to the core walls are to be expected.
In addition to this, wax is a material which is brittle and has low inherent stability. When the mold is opened, tensile stresses arise in the solidified wax and there is therefore a danger of cracks forming, even when the walls of the core arrangements of the mold are provided with a taper.
A device for removing shaped articles from a shaping housing is known from Swiss Patent Specification No. 548,240. There, a core consisting of pressed sand for producing hollow castings is removed from a shaping housing by means of a diaphragm-like elastomeric disk actuated by compressed air.
The device of said Swiss Patent Specification is suitable for sand casting in which the surface-to-volume ratio of the shaped articles is comparatively smaller than in cast wax models. Moreover in sand casting the requirements demanded in the operation of releasing the shaped article from the shaping housing are nowhere near as stringent as in the shaping of thin-walled wax models in a mold.
The non-destructive release of solidified thin-walled wax models from the walls of the core arrangements therefore presents substantially greater problems than in sand casting and can be carried out only inadequately by the devices known at the present time in the foundry industry.